Colloidal systems of cyanoethylated starch and their use



COLLOllDAL SYSTEMS F CYANGETHYLATED STARCH AND THEM USE Thomas E. Sample, .lia, La Marque, Tex, assignor to Monsanto Chemical Company, St. Louis, Mo, a corporation of Delaware No Drawing. Application January 3, 1956 Serial No. 556,792

17 tillaims. (Cl. 106-213) This invention relates to colloidal systems of cyanoethylated starch, water and water-miscible, low molecular weight, aliphatic ketones and the use of such systems for impregnating cellulosic materials.

Starch-water mixtures are commonly used as impregnants for cellulosic materials such as cloth and paper. The resultant starch-coated cellulosic material is susceptible to attack by microorganisms, water and other solvents. To eliminate this deficiency it is common practice to further treat such starch-impregnated cellulosic materials with another impregnant for the purpose of decreasing the susceptibility of the cellulosic product to deterioration due to the attack of water, other solvents and microorganisms. This double impregnated technique is obviously costly.

The cyanoethyl ethers of starch are well known in the art. Those containing a degree of substitution of from 1.5 to 2.0, that is, from about 1.5 to 2.0 cyanoethyl ether groups per glucose unit, are extremely resistant to attack by microorganisms, water and other solvents. Due to the insolubility of such cyanoethyl ethers of starch in Water and common organic solvents, it has not been possible to satisfactorily impregnate cellulosic materials with these cyanoethyl ethers of starch according to methods heretofore used.

It is an object of this invention to provide improved colloidal sols of cyanoethyl ethers of starch. It is a further object to provide cellulosic materials impregnated With cyanoethyl ethers of starch and a process for producing such impregnated cellulosic materials. Other objects will become apparent from a description of the invention.

It has now been discovered that, while cyanoethyl ethers of starch containing from about 1.5 to 2.0 cyanoethyl 'of starch containing from about 1.5 to about 2.0 cyanoethyl ether groups per glucose unit, in a solvent mixture of a water-miscible, low molecular weight, aliphatic ketone and water, said solvent mixture containing an amount of water dependent upon the number of cyanoethyl ether groups per glucose unit, said amount of water being present in a minimum amount varying from about 1% by weight of solvent mixture for a starch containing about 2.0 cyanoethyl ether groups per glucose unit to a minimum of about 12% by weight of solvent mixture for a starch containing about 1.5 cyanoethyl ether groups per glucose unit and in a maximum amount varying from about 49% by Weight of solvent mixture for a starch containing about 2.0 cyanoethyl ether groups per glucose unit to a maximum amount of approximately 55% by weight of solvent mixture for a starch containing about 1.5 cyanoethyl ether groups per glucose unit.

The unusual nature of the colloidal sols of this invention was established by a series of very simple tests. Colloidal sols of cyanoethylated starch having varying degrees of substitution were prepared in water-acetone mixtures containing from about 5% to about 30% Water.

The concentration of the cyanoethylated starch in such samples was about 7%. Duplicate samples were then titrated with water to establish the maximum concentration of water in the solvent mixture at which irreversible precipitation occurred. Similar duplicate samples Were then titrated with acetone to establish the minimum concentration of Water in the solvent mixture at which irreversible precipitation occurred. Results are indicated in the following table:

EXTREME LIMITS OF STABILITY OF THE OOLLOIDAL SYSTEM.CYANOETHYLATED STAROH WATER ACE- TONE (30 0.)

cyanoethyl ether groups per glucose unit;

(D. SJ) V 1.3% min. to 49% max. 4% min. to 53% max. 12% min. to 55% max.

1 cyanoethyl ether groups per glucose unit.

A solvent mixture of water and acetone containing water below the minimum or above the maximum specified in the foregoing table cannot be used to prepare a colloidal sol for a cyanoethyl ether of starch of the degree of substitution indicated. Similar results are obtained using other low molecular weight, Water-miscible, aliphatic ketones such as methyl ethyl ketone, diethyl ketone and cyclohexanone.

From the standpoint of this invention, the critical factor in all of these systems is the ratio of water to acetone and not the concentration of the cyanoethylated starch. The results indicate that as the number of cyanoethyl ether groups per glucose unit varies, the amount of Water necessary in the water-acetone mixture to prepare stable colloidal sols also varies. As the degree of substitution increases, both the minimum and the maximum tolerable limits of water in the water-acetone mixture decrease. Within the limits of this invention, the solvent mixture of acetone and water used to prepare colloidal sols of cyanoethylated starch having a degree of substitution of about 2.0 must contain water varying from a minimum amount of about 1% by weight of solvent mixture to a maximum of about 49% by weight of solvent mixture. A solvent mixture of acetone and water used to prepare a colloidal sol of a cyanoethyl ether of starch containing about 1.5 cyanoethyl ether groups per glucose'unit must contain water in a minimum amount of about 12% by weight of solvent mixture to a maximum amount of about 55% by weight of solvent mixture.

The colloidal dispersions of this invention are easily prepared. The cyanoethyl ether of starch is merely mechanically dispersed in the solvent mixture of water and a low molecular weight, Water-miscible, aliphatic ketone. While the foregoing results were obtained using a cyanoethyl ether of corn starch, cyanoethyl ethers of sago, tapioca, potato, Wheat and rice starches can also be used.

The colloidal sols of this invention can be used to' impregnate cellulosic materials, rendering them less susceptible to deterioration due to attack of water, other solvents and microorganisms. In accordance with this invention, improved cellulosic products are obtained by impregnating the cellulosic material with the colloidal sols of this invention, drying the impregnated cellulosic material and then calendering the cellulosic material. Cellulosic materials that can be impregnated by the proccloth, holland cloth and the like.

ess of this invention include paper and fabrics, particularly woven cotton fabrics suitable for use as tracing The following examples illustrate this process:

Example I A colloidal sol is prepared containing approximately 10% by weight of a cyanoethyl ether of starch having a degree of substitution of 1.95 in a solvent mixture of water and acetone containing 10% by weight of water. This colloidal sol is knife-coated onto thin stock paper and the impregnated paper dried at 110 F. The impregnated paper is then calender-ed by pressing with a hot iron at about 310 F. The surface of the paper thus obtained is highly glazed. The paper is extremely flexible and highly resistant to attack by water, other organic solvents and microorganisms.

Example II The procedure set forth in Example I is repeated using a cyanoethyl ether of starch having a degree of substitution of 1.78. Comparable results are obtained.

Example Ill The procedure set forth in Example I is repeated using a colloidal sol composed of a 10% by weight colloidal dispersion of a cyanoethyl ether of starch having a degree of substitution of 1.51 in a solvent mixture of water and acetone containing 20% by weight of water. Comparable results are obtained.

Example IV A colloidal sol is prepared containing approximately 10% by weight of a cyanoethyl ether of starch having a degree of substitution of 1.95 in a solvent mixture of water and acetone containing 10% by weight of water. A bleached cotton fabric weighing 1.9 ounces per square yard and having 85 warp ends and 87 filling yarns per inch is impregnated by immersion in this colloidal sol. The impregnated fabric is dried at about 100 F. for about 20 minutes. The impregnated fabric is then given two passes through a three-roll friction calender maintained at a temperature of about 320 F. The calendered fabric has exceptional utility as tracing cloth. The surface of the fabric is smooth and highly glazed and is extremely resistant to water, organic solvents and microorganisms.

Example V The procedure set forth in Example IV is repeated using a cyanoethyl ether of starch having a degree of substitution of 1.78. Comparable results are obtained.

Example VI The procedure set forth in Example IV is repeated using a colloidal sol composed of a 10% by Weight 001- loidal dispersion of a cyanoethyl ether of starch having a degree of substitution of 1.51 in a solvent mixture of water and acetone containing 20% by weight of water. Comparable results are obtained.

In all of the preceding examples, acetone can be replaced with any other low molecular weight, water-miscible, aliphatic ketones such as methyl ethyl ketone, diethyl ketone, cyclohexanone, etc.

The colloidal sols of this invention can be applied to cellulosic materials in any of various ways well known to those skilled in the art. Knife-coating, roll-coating or immersion of the cellulosic material in the sol are all suitable methods of treatment. Repeated immersions with drying between immersions are particularly useful.

The quantity of the cyanoethyl ether of starch in the colloidal sol used to treat cellulosic materials in accordance with this invention can be substantially varied. In general, from about 5% to about 30% by weight of the cyanoethyl ether of starch based on total composition of the sol is used. Higher or lower concentrations can be used in particular applications if desired. If desired, plasticizers may be added to the colloidal sol to alter the flexibility characteristics of the finished impregnated product.

Various conditions of drying and calendering of the impregnated cellulosic material can be used. For example, the impregnated cellulosic material, such as cloth, may be dried at any temperature which drives off the solvent contained in the impregnating dispersion, but it is preferably dried at temperatures which allow the solvent to be released at such a rate whereby formation of blisters or bubbles on the treated surface is avoided. If speed of drying is unimportant, the impregnated cellulosic material can be dried at normal room temperatures. The impregnated material can be dried satisfactorily, for example, at temperatures varying between to F.

Calendering may be carried out by using other means and conditions than those described above. Hand ironing and friction calendering are particularly suitable. in general, the impregnated material is super-calendered at temperatures and pressures which will cause the impregnant to soften or flow into a substantially continuous film or surface. Suitable temperatures for super-calendering vary between about 275 F. to about 330 F. Other temperatures can be used when different effects are desired.

The term consisting essentially of which appears in the claims hereof is intended to refer to a composition in which the total amounts of the components set forth in the claim constitutes the predominant proportion in the composition. Such term is not intended to exclude the presence of materials such as plasticizers or modifiers or other materials which may be present and do not adversely affect the dispersion. However, the term is intended to exclude the presence of materials which so change the character of the composition that it can no longer be regarded as a dispersion of a cyanoethyl ether of starch.

What is claimed is:

1. A composition consisting essentially of a colloidal dispersion of a cyanoethyl ether of starch containing from about 1.5 to about 2.0 cyanoethyl other groups per glucose unit, in a solvent mixture of water and a ketone chosen from the group consisting of the watermiscible, low-molecular-weight, aliphatic and alicyclic ketones, water being present in a minimum amount varying from about 1% by weight of solvent mixture for a starch containing about 2.0 cyanoethyl other groups per glucose unit to a minimum amount of about 12% by weight of solvent mixture for a starch containing about 1.5 cyanoethyl ether groups per glucose unit and in a maximum amount varying from about 49% by weight of solvent mixture for a starch containing about 2.0 cyanoethyl ether groups per glucose unit to a maximum amount of about 55% by weight of solvent mixture for a starch containing about 1.5 cyanoethyl ether groups per glucose unit.

2. A composition as described in claim 1, wherein the ketone is acetone.

3. A composition as described in claim 1, wherein the ketone is methyl ethyl ketone.

4. A composition as described in claim 1, wherein the ketone is cyclohexanone.

5. A composition consisting essentially of a colloidal dispersion of a cyanoethyl ether of starch containing about 2.0 cyanoethyl ether groups per glucose unit, in a solvent mixture of acetone and Water, said solvent mixture containing water in an amount of from about 1% by weight to about 49% by Weight of solvent mixture.

6. A process for the preparation of improved cellulosic materials which comprises impregnating a cellulosic material With a composition as defined in claim 1, drying said impregnated cellulosic material, and then calendering said cellulosic material.

7. A process for the preparation of improved cellulosic fabrics which comprises impregnating a cellulosic fabric with a composition as defined in claim 1, drying said impregnated cellulosic fabric, and then calendering said cellulosic fabric.

8. A process for the preparation of improved cotton fabrics which comprises impregnating a cotton fabric with a composition as defined in claim 1, drying said impregnated cotton fabric, and then calendering said cotton fabric.

9. A process for treating paper which comprises impregnating paper with a composition as defined in claim 1, drying said impregnated paper, and then calendering said paper.

10. A process for the preparation of improved cellulosic materials which comprises impregnating a cellulosic material with a composition consisting essentially of a colloidal dispersion of a cyanoethyl ether of starch containing from about 1.5 to about 2.0 cyanoethyl groups per glucose unit in a solvent mixture of acetone and water, water being present in a minimum amount varying from about 1% by weight of the solvent mixture for a starch containing about 2.0 cyanoethyl groups per glucose unit to a minimum amount of about 12% by weight of the solvent mixture for a starch containing about 1.5 cyanoethyl groups per glucose unit and in a maximum amount varying from about 49% by weight of the solvent mixture for a starch containing about 2.0 cyanoethyl ether groups per glucose unit to a maximum amount of about 55% by weight of the solvent mixture for a starch containing about 1.5 cyanoethyl groups per glucose unit, drying said impregnated cellulosic material and then calendering said cellulosic material.

11. A process for the preparation of improved cellulosic fabrics which comprises impregnating a cellulosic fabric with a composition consisting essentially of a colloidal dispersion of a cyanoethyl ether of starch containing from about 1.5 to about 2.0 cyanoethyl groups per lucose unit in a solvent mixture of acetone and water, Water being present in a minimum amount varying from about 1% by weight of the solvent mixture for a starch containing about 2.0 cyanoethyl groups per glucose unit to a minimum amount of about 12% by weight of the solvent mixture for a starch containing about 1.5 cyanoethyl groups per glucose unit and in a maximum amount varying from about 49% by weight of the solvent mixture for a starch containing about 2.0 cyanoethyl ether groups per glucose unit to a maximum amount of about 55% by weight of the solvent mixture for a starch containing about 1.5 cyanoethyl groups per glucose unit, drying said impregnated cellulosic fabric and then calendering said cellulosic fabric.

12. A process for the preparation of improved cotton fabrics which comprises impregnating a cotton fabric with a composition consisting essentially of a colloidal dispersion of a cyanoethyl ether of starch containing from about 1.5 to about 2.0 cyanoethyl groups per glucose unit in a solvent mixture of acetone and water, water being present in a minimum amount varying from about 1% by weight of the solvent mixture for a starch containing about 2.0 cyanoethyl groups per glucose unit to a minimum amount of about 12% by weight of the solvent mixture for a starch containing about 1.5 cyanoethyl groups per glucose unit and in a maximum amount varying from about 49% by weight of the solvent mixture for a starch containing about 2.0 cyanoethyl ether groups per glucose unit to a maximum amount of about 55% by weight of the solvent mixture for a starch containing about 1.5 cyanoethyl groups per glucose unit, drying said impregnated cotton fabric and then calendering said cotton fabric.

13. A process for treating paper which comprises impregnating paper with a composition consisting essentially of a colloidal dispersion of a cyanoethyl ether of starch containing from about 1.5 to about 2.0 cyanoethyl groups per glucose unit in a solvent mixture of acetone and water, water being present in a minimum amount varying from about 1% by weight of the solvent mixture for a starch containing about 2.0 cyanoethyl groups per glucose unit to a minimum amount of about 12% by weight of the solvent mixture for a starch containing about 1.5 cyanoethyl groups per glucose unit and in a maximum amount varying from about 49% by Weight of the solvent mixture for a starch containing about 2.0 cyanoethyl ether groups per glucose unit to a maximum amount of about 55% by weight of the solvent mixture for a starch containing about 1.5 cyanoethyl groups per glucose unit, drying said impregnated paper and then calendering said paper.

14. A process for the preparation of improved cellulosic materials which comprises impregnating a cellulosic material with a composition consisting essentially of a colloidal dispersion of a cyanoethyl ether of starch containing about 2.0 cyanoethyl groups per glucose unit in a solvent mixture of acetone and water, said solvent mixture containing water in an amount from about 1% to about 49% by weight of the solvent mixture, drying said impregnated cellulosic material, and then calendering said cellulosic material.

15. A process for the preparation of improved cellulosic fabrics which comprises impregnating a cellulosic fabric with a composition consisting essentially of a colloidal dispersion of a cyanoethyl ether of starch containing about 2.0 cyanoethyl groups per glucose unit in a solvent mixture of acetone and Water, said solvent mixture containing water in an amount from about 1% to about 49% by weight of the solvent mixture, drying said impregnated cellulosic fabric, and then calendering said cellulosic fabric.

16. A process for the preparation of improved cotton fabrics which comprises impregnating a cotton fabric with a composition consisting essentially of a colloidal dispersion of a cyanoethyl ether of starch containing about 2.0 cyanoethyl groups per glucose unit in a solvent mixture of acetone and Water, said solvent mixture containing water in an amount from about 1% to about 49% by weight of the solvent mixture, drying said impregnated cotton fabric, and then calendering said cotton fabric.

17. A process for treating paper which comprises impregnating paper with a composition consisting essentially of a colloidal dispersion of a cyanoethyl ether of starch containing about 2.0 cyanoethyl groups per glucose unit in a solvent mixture of acetone and water, said solvent mixture containing water in an amount from about 1% to about 49% by weight of the solvent mixture, drying said impregnated paper, and then calendering said paper.

OTHER REFERENCES Hackhs Chemical Dictionary, 3rd edition (1944), page 30. 

1. A COMPOSITION CONSISTING ESSENTIALLY OF A COLLOIDAL DISPERSION OF A CYANOETHYL ETHER OF STARCH CONTAINING FROM ABOUT 1.5 TO ABOUT 2.0 CYANOETHYL ETHER GROUPS PER GLUCOSE UNIT, IN A SOLVENT MIXTURE OF WATER AND A KETONE CHOSEN FROM THE GROUP CONSISTING OF THE WATERMISCIBLE, LOW-MOLECULAR-WEIGHT, ALIPHATIC AND ALICYLIC KETONES, WATER BEING PRESENT IN A MINIMUM AMOUNT VARYING FROM ABOUT 1% BY WEIGHT OF SOLVENT MIXTURE FOR A STARCH CONTAINING ABOUT 2.0 CYANOTHYL ETHER GROUPS PER GLUCOSE UNIT TO A MINIMUM AMOUNT OF ABOUT 12% BY WEIGHT OF SOLVENT MIXTURE FOR A STARCH CONTAINING ABOUT 1.5 CYANOETHYL ETHER GROUPS PER GLUCOSE UNIT AND IN A MAXIMUM ANOUNT VARYING FROM ABOUT 49% BY WEIGHT OF SOLVENT MIXTURE FOR A STARCH CONTAINING ABOUT 2.0 CYANOETHYL ETHER GROUPS PER GLUCOSE UNIT TO A MAXIMUM AMOUNT OF ABOUT 55% BY WEIGHT OF SOLVENT MIXTURE FOR A STARCH CONTAINING ABOUT 1.5 CYANOETHYL ETHER GROUPS PER GLUCOSE UNIT. 